1. Field of the Invention
The present invention is in the field of computer hosted memory cards and associated hard disk interfaces and pertains particularly to methods and apparatus for eliminating intermediate data bussing and bridging requirements between a removable data storage element like a memory device or a computer hard disk.
2. Discussion of the State of the Art
In the field of computer components including removable memory devices, there has been much advancement in the technology and improvements continue. In a typical computer system, a system bus or host bus is the main data bus used to communicate between components. With the advent of removable memory devices and peripheral devices other types of computer busses were developed to enable smooth data transmission without interrupting CPU processing. Most computer systems today include a series of computer busses that branch off of the main bus or system bus. These busses include a peripheral component interconnect (PCI) bus and universal serial bus (USB), both well known in the art in several different variations.
Most modern computing systems include a disk drive that has a built in disk controller. The most common implementation is advanced technology attachment (ATA), which includes a protocol known as programmed input/output (PIO) for data transfer. Most modern ATA systems use direct memory access (DMA) protocol for data transfer.
In prior art, removable memory devices like secure digital or universal serial bus solid-state memory devices are attached to an intermediate disk channel, then to a disk controller, then to a PCI channel connected to the host bus before the operating system can recognize and interact with the device. From a standards point of view the current method of interfacing to a removable solid-state memory device is acceptable and works well. However, from a system performance point of view, there is a performance loss any time an intermediate channel or bus is imposed between a data storage element like a removable solid-state memory device and a host computer main system bus.
FIG. 1 is a block diagram of a removable secure digital (SD) card 100 adapted for use with a personal computer (PC) according to prior art. SD card 101 is typically used in video recording and playback devices, mobile phones, digital cameras, and other hand-held devices. More recently, computers have been provided with SD card slots on their exterior surface housings for accepting SD cards. In this example, SD card 100 plugs into a host computer 101. SD card 100 has a flash memory (MEM) module 102, a flash controller 104 for controlling how the host uses flash MEM 102, and a disk interface 105 for providing interface capability to the hard disk drive of the host computer 101.
Host computer 101 has a PC board 111, typically a motherboard that has a peripheral component interconnect (PCI) interface 109 as is typical with most computer hosts. The PCI interface communicates to the motherboard via a PCI channel 110, and through disk control registers 108 to a disk controller 107. Disk controller 107 must communicate to flash controller 104 through disk interface 105 on SD card 100 via disk channel 106.
All of these components must be present so that the host operating system immediately recognizes flash MEM 102 as a system disk without requiring installation and/or pre-activation of special software drivers or other software that registers the device with the host registry system on the computer and enables the device for normal use. The requirement of so many interfacing components between the peripheral storage element and the system may contribute to some limitation in performance, more particularly, the speed at which flash memory 102 may be read and written to.
FIG. 2 is a block diagram of a removable jump drive or “flash drive” 200 adapted for use with a host computer according to prior art. Jump drive 200, also known in the art as a “thumb” drive or “key chain” drive is a universal serial bus (USB) device that may be plugged into a to a USB port on host computer 201. Jump drive 200 has a flash MEM 202 for persistent data storage. Jump drive 200 also has a flash controller 204 that controls how data is stored and accessed. Controller 204 communicates on one side to flash MEM 202 via an address/data control channel 203 and on the other side to a universal serial bus (USB) interface 205.
Host computer 201 communicates with jump drive 200 through a USB channel 206. Host computer 201 has a USB controller 207 and bus control registers 208 between USB interface 205 on drive 200 and a PCI interface 209. Host computer 201 has a PC board, typically a motherboard that communicates to the USB port through PCI interface 209 via a PCI channel 210. In this example, The USB components must be in place between the PCI interface on host computer 201 and the flash controller 204 in order for flash MEM 202 to be recognized by the host computer without requiring software driver installation and pre-configuration or pre-activation tasks similar to those tasks required with the SD card described further above with respect to FIG. 1.
What is clearly needed in the art is unified controller that connects a removable or non-removable solid-state memory device directly to a host system bus without requiring any intermediary bus or channel between the device and the main system bus. Such a controller could be provided as part of the removable or non-removable media reducing overall complexity of the interfacing requirements, improving performance of read and write on the device, and enabling overall reduction of physical space required implementing the interface.